May 31, 2013

If current trends continue, the trout, salmon and other native freshwater fish in California will likely become extinct within the next century due to climate change.

A new study from the Center for Watershed Sciences at the University of California, Davis (UCDavis), assessed how vulnerable each freshwater species in California is to climate change and estimated the likelihood that those species would become extinct in 100 years.

Of 121 native fish species, the research team found that 82 percent are likely to be driven to extinction or very low numbers as climate change accelerates the decline of already depleted populations. The study, published in PLoS ONE, found that only 19 percent of the 50 non-native fish species in California face a similar extinction risk.

“If present trends continue, much of the unique California fish fauna will disappear and be replaced by alien fishes, such as carp, largemouth bass, fathead minnows and green sunfish,” Peter Moyle, a professor of fish biology at UC Davis, said in a statement. Moyle has been documenting the biology and status of California fish for the past 40 years.

“Disappearing fish will include not only obscure species of minnows, suckers and pupfishes, but also coho salmon, most runs of steelhead trout and Chinook salmon, and Sacramento perch,” Moyle added.

Cold water fish, such as salmon and trout, are at particular risk of extinction, the research team found. Non-native species, however, are expected to thrive; although some will lose their habitats during extreme droughts and low-flow summer months.

The study lists the top 20 California fish most likely to become extinct in the state within the next 100 years as a result of climate change. Asterisks in the list denote a species that is already listed as threatened or endangered. The species below are listed in order of vulnerability, with No. 1 being the most vulnerable.

1. Klamath Mountains Province summer steelhead

2. McCloud River redband trout*

3. Unarmored threespine stickleback

4. Shay Creek stickleback

5. Delta smelt*

6. Long Valley speckled dace

7. Central Valley late fall Chinook salmon

8. Kern River rainbow trout

9. Shoshone pupfish

10. Razorback sucker*

11. Upper Klamath-Trinity spring Chinook salmon

12. Southern steelhead*

13. Clear Lake hitch

14. Owens speckled dace

15. Northern California coast summer steelhead

16. Amargosa Canyon speckled dace

17. Central coast coho salmon*

18. Southern Oregon Northern California coast coho salmon*

19. Modoc sucker*

20. Pink salmon

The researchers found that global declines of freshwater fishes have been caused by climate change and human-caused degradation of aquatic habitats, especially in regions with arid or Mediterranean climates. These declines are creating a major challenge for conservation efforts. Until now, however, there has been little research in the scientific literature related to the status of most fish species, particularly native ones of little economic value.

Moyle and his team saw a need for a rapid and repeatable method of determining the climate change vulnerability of different species, and they expect the new method to be useful for conservation planning.

“These fish are part of the endemic flora and fauna that makes California such a special place,” said Moyle. “As we lose these fishes, we lose their environments and are much poorer for it.”